Carpenter ants (Camponotus) are large insects known for excavating wood to create nesting galleries for their colonies. They do not eat the wood. While they are famously associated with wood, their use of soil is more nuanced. Proper identification of the species and nesting location is important because an infestation often signals underlying structural moisture issues.
Primary Nesting Habits
Carpenter ants prefer to establish nests in wood that is soft, usually due to high moisture or decay. This softened wood allows them to more easily carve out smooth, clean tunnels and chambers. The presence of moisture is a strong indicator of a suitable nesting site for the main, or parent, colony.
Colony structure is divided into two primary types: parent and satellite nests. The parent colony houses the queen, eggs, and young, requiring consistent, high humidity to prevent the eggs from drying out. Parent colonies are often found outdoors in decaying tree stumps, logs, or in structural wood suffering from water damage.
As the colony population expands, workers may establish one or more satellite nests nearby. These nests house workers, mature larvae, and pupae, but lack the queen or eggs. Since they do not need to protect eggs, satellite colonies can be established in drier locations, such as wall voids, hollow doors, or sound wood within a home.
Excavating wood produces a distinctive waste material called frass, which is pushed out of the nest galleries. Frass resembles fine sawdust and is often mixed with fragments of dead ants and discarded insect body parts. Piles of frass near wood are one of the most visible signs of an active wood-nesting colony.
When Carpenter Ants Use the Ground
Carpenter ants do not typically excavate nests directly in soil, but they frequently use the ground as a foundation for their colonies. The ground becomes a viable nesting location when it contains embedded wood materials, such as stumps, fallen logs, or buried construction debris. Parent colonies are often found outdoors in decaying wood lying on or partially buried beneath the soil surface.
In these instances, the ants are excavating the wooden material within the soil matrix, not tunneling through the soil itself. The soil provides a stable, protected, and often moist environment that facilitates the wood decay they seek. Some opportunistic species also utilize the soil as a temporary shelter or a route to a more suitable nesting material.
Colonies may be found under stones, landscape timbers, or loose debris resting on the ground, using the soil beneath for cover. These ground-adjacent nests can function as satellite colonies or foraging tunnels connected to a main nest elsewhere. The distinction is that the main structural damage is still being caused to the wood material, not the soil.
Distinguishing Carpenter Ants from Common Ground-Nesting Species
Differentiating carpenter ants from other common ground-nesting species is important because of the threat they pose to wooden structures. Carpenter ants are among the largest ants found in homes, with workers ranging from 6 to 13 millimeters in length. They are typically black, or sometimes black and red, and exhibit a distinct physical profile.
When viewed from the side, a carpenter ant has a single segment, or node, connecting the abdomen and thorax. Its thorax is evenly rounded and smoothly convex. This uniform, rounded thoracic profile is a reliable visual characteristic that separates them from many other ant species, which often have an uneven or notched profile.
The evidence left behind by the nest is the most telling difference between the species. Ground-nesting ants, such as pavement ants, excavate soil, leaving behind mounds of fine dirt or sand at the nest entrance. Conversely, carpenter ants leave behind frass, which is composed of wood shavings and insect parts, with no soil present.
Actionable Steps for Detection and Control
Homeowners suspecting a carpenter ant presence must first focus on locating the nest, which can be difficult due to its hidden nature. A good starting point is to inspect areas prone to moisture, such as around leaky pipes, window sills, and poorly ventilated crawl spaces. Tapping on wooden structures and listening for a faint, dry rustling sound can indicate an active nest just beneath the surface.
Observing foraging trails, especially at night when carpenter ants are most active, can lead directly back to the nest location. Workers may travel up to 100 yards from the nest in search of food, which includes sweets and proteins. Following a trail of ants can reveal the entry point into the structure or the location of an outdoor parent colony in a log or stump.
The most effective long-term control strategy is moisture management, as this removes the environment that attracts the ants. This involves several steps:
- Fixing all water leaks promptly.
- Ensuring gutters are clear.
- Replacing any wood that has sustained moisture damage.
- Removing potential outdoor nesting sites, such as dead tree stumps and logs.
Control methods focus on delivering an insecticide directly to the nest or using baits that workers carry back to the colony. Targeted application of insecticidal dust into voids where the ants are nesting is highly effective once the nest is located. For extensive or inaccessible infestations, consulting with a pest management professional is often the most reliable method for complete eradication.